The Long Term Evolution (LTE) system has been standardized in the 3rd Generation Partnership Project (3GPP) as a global standard for radio communication systems. In LTE, the transmission bandwidth for radio communication between a radio communication base station and a radio communication terminal (mobile terminal) is allocated into resource blocks (RB) as minimal units. The bandwidth of a resource block is 180 kHz. For each subframe (1 ms), the radio communication base station schedules the radio resource allocated to each mobile terminal. In the present disclosure, a radio communication base station is abbreviated as a “base station” as appropriate, and a radio communication terminal (mobile terminal) is abbreviated as a “terminal” as appropriate.
In the LTE system, in order to use the radio communication band efficiently, the base station schedules radio resources allocated to the terminals based on the transmission request data size and on the radio quality between the base station and the terminals. More resource blocks are allocated to a terminal with a large transmission data size, and fewer resource blocks are allocated to a terminal with a small transmission data size. The question of whether radio quality between the terminals and the base station is good, i.e. whether the Signal to Interference and Noise Ratio (SINR) is large, is also considered when scheduling radio resources allocated to the terminals.
Using a reference signal, radio quality is measured for both the uplink, i.e. data transmission from the terminal to the base station, and the downlink, i.e. data transmission from the base station to the terminal. The radio quality of the downlink is determined by the terminal measuring the SINR for a reference signal transmitted from the base station to the terminal. The terminal provides feedback on the radio quality to the base station by transmitting the measured SINR in correspondence with a Channel Quality Indicator (CQI) to the base station. The terminal reports the CQI to the base station periodically. The radio quality of the uplink is determined by the base station measuring the SINR for a reference signal transmitted from the terminal to the base station (for example, see Non-patent Literature 1). In this way, based on the radio quality at the latest report time, the base station schedules the radio resources allocated to the terminals. The radio communication band can thus be used efficiently.
A technique for allocating radio resources to a group of base stations has also been proposed (for example, see Patent Literature 1). According to the technique disclosed in Patent Literature 1, when the terminal is moving at high speed, or even when many terminals are connected to the base stations in a short period of time, it is possible to reduce the processing load for allocating radio resources used in communication between the plurality of base stations and terminals, for authentication, and the like. Accordingly, with the technique disclosed in Patent Literature 1, the base station can allocate channels to terminals efficiently and at high speed.